Presentation Transcript

CORROSION :

CORROSION

CORROSION :

CORROSION Corrosion is a chemical change, in which a metal loses its properties because of a chemical reaction with its environment.
Corrosion is a very slow process, can take decades depending on the metal involved.
Corrosion looks different for different types of metals.

IRON (Rusting) :

IRON (Rusting) The corrosion of iron-based metals is called RUSTING
Iron reacts with oxygen to form IRON OXIDE
The oxygen can come from AIR or WATER

IRON (Rusting) :

IRON (Rusting) Rusting iron is POROUS

What’s Porous? :

What’s Porous?

What’s Porous? :

What’s Porous?

IRON (RUSTING) :

IRON (RUSTING) So What?
Rusted metal will absorb water and “flake off”
This exposes fresh un-rusted metal to water or oxygen
This new metal will rust
Costs billions of dollars

Rust is Porous :

Rust is Porous

ALUMINUM :

ALUMINUM Reacts with oxygen in the air to make ALUMINUM OXIDE The aluminum develops a layer of rust, preventing further corrosion.

SILVER :

SILVER

SILVER :

SILVER Silver does not rust, but tarnishes very slowly.
Silver reacts with hydrogen sulfide found in food or water
In this reaction, silver turns into silver sulfide.
Silver Sulfide:
Called “tarnish”
A blue/black colour